Is the Air Really Less Polluted Than Before?

– 06 November 2019 – Science

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In a column published on November 6, 2019 in L’Express, Laurent Alexandre uses figures from AirParif to justify a claim that air pollution is in free fall. But his interpretation of the data, while not inaccurate, is flawed.

“That’s not a very fair presentation of things. There are a lot of things that call out to us“, alerts Céline Delysse, head of communication for the AirParif organization, contacted by Numerama. On November 6, 2019, Laurent Alexandre published a column in the newspaper L’Express entitled “Air pollution collapses“. In his text, the famous climatoptimistic, surgeon, business man and founder of Doctissimo, relies on figures and statements by AirParif to legitimize his remarks. Problem: even AirParif does not agree with what Laurent Alexandre says.

The figures he invokes in his column are interpreted as biased as they are incomplete, if not completely incomprehensible. The first alarm bell to be sounded is generalization: whether in the title or in the first paragraph, the author frames his approach in a national manner, on a French scale. “It seems to speak of AirParif as an entity that would reflect the whole of France, but this is not the case, we look at the Ile-de-France region, Céline Delysse recalls. Even on the improvements that have been noted, they should not be generalized. To say that air quality is improving everywhere would not be true“.

Air pollution is estimated to cause 48,000 deaths a year in France. // Source: MaxPixel

Biased selected data

AirParif also invites you to take a closer look at the way you select data, the way you make it talk. From the beginning of his column, Laurent Alexandre announces with great pomp and circumstance that SO₂ (sulphur dioxide) has dropped significantly. Pierre Pernot, an engineer at AirParif, is keen to qualify the value to be attached to this observation: “It has been a long time since there has been an air quality problem with sulphur dioxide. It no longer needs to be measured. So it is not sulphur dioxide which is an indicator of air quality.»

Same pattern for many other data invoked by Laurent Alexandre. ” There are pollutants that are no longer part of the majorconcerns today,” adds Céline Delysse. Indeed, the situation has changed enormously in recent decades and some pollutants are disappearing. Many industries that were once located in the Paris Region have now left. Not to mention that regulatory provisions have been effective: if Laurent Alexandre claims that the disappearance of lead has been hidden, this is not the case because, as Pierre Pernot explains, “is the result of its ban in gasoline, just as sulphur dioxide disappears because it has been removed fromfuels”.

Pollutants such as ozone are on the rise…

This does not mean that everything is fine and that air pollution “collapses“. In addition to the pollutants already listed, new pollutants are emerging. For example, while Laurent Alexandre puts forward figures that speak little, he gives only one sentence to ozone. Let’s quote him: “Ozone levels remain unsatisfactory“. However, the scientific reality is far beyond mere dissatisfaction. AirParif engineer Pierre Pernot tells Numerama that “pollutants such as ozone are rather atincrease”. The health risk threshold is “exceeded in the entire Île-de-Francearea”, adds Cécile Delysse.

Another misuse of the data by Laurent Alexandre challenged AirParif. Again, let’s quote: ” Fine particles, which are the constituents of black smoke, have fallen by 80% since 1950“. Pierre Pernot’s reaction was not long in coming: ” That’s not true.. In 1950, there were no measurements of PM10fine particulate matter. So the problem here is the rhetorical ambiguity of the sentence. Because although black smoke does indeed contain fine particles, not all fine particles are extracted from black smoke. A decrease in fine particles is indeed taking place, but rather in the order of 33 to 40% between 2005 and 2018 according to the figures sent to us by Airparif. For some years now, there has also been concern about so-called “ultrafine” particles, the detailed study of which has only just begun.

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” The air remains polluted ”

Beyond the fact that Laurent Alexandre has poorly selected the data, it turns out that they are of little relevance by being put forward as they are. “The emission of the pollutant should not be confused with its source and concentration,” notes Céline Delysse. Numbers need to be replaced in context. Although air quality has improved slightly in Île-de-France in recent years we are starting from a very long way off, so an improvement ” does not mean that people in Île-de-France are not exposed to levels that put their healthat risk”.

Ten million people in the Paris Region are exposed to a high level of fine particles. ” Despite an improving trend, the daily and annual limit values for fine particles are still exceeded in the vicinity of road traffic“, Cécile Delysse tells Numerama. 85% of people in the Ile-de-France region are exposed to ozone. In short, ” the air remains polluted“, adds Pierre Pernot. For most pollutants, “we are still well above the World Health Organization’srecommendations” in Île-de-France. Moreover, France was recently condemned by the Court of Justice of the European Union for failing to comply with air quality standards.

An upward revision of the health impact of pollution

For the AirParif team, the improvements to be noted are obviously positive, but “this evolution is not going fast enough“, awareness must be maintained. Especially since Pierre Pernot would like to specify that ” health assessments show rather an upward revision of the health impact of pollution. Therefore, air quality data should be used with great caution.“. Air pollution is estimated to cause 48,000 premature deaths in France every year. And the scientific community is increasingly questioning the health risks of other components that are still poorly identified, such as ultrafine particles and many others. “There is a need for real vigilance, because not only are the levels unsatisfactory, but there are emerging pollutants that need to be documented“,

In fact, when Laurent Alexandre states in his tweet that ” the most striking ecological phenomenon of the last 50 years is the rapid free fall of air pollution“, this is obviously false. The low scientific value of his column is a reminder that the great figures of climatoscepticism are above all characterized by incompetence. Laurent Alexandre is used to unsourced or misunderstood data, as was the case when he confused fire starts and fires in the Amazon this summer.

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